Moved from IMHO to CS.
It’s not exactly soda, since it isn’t carbonated, but Hawaiian Punch makes a “Light” version that is very tasty. It’s sweetened with Splenda.
I only like diet sodas and found that Coke Zero tastes just like that vile Coke Classic, so you might like that.
I don’t like Diet Dr Pepper because IMO it tastes too much like regular soda.
If you like root beer, you can fill a glass 95% full with Diet Coke, and then top it off with root beer and it tastes just like root beer. It’s almost creepy.
A&W Diet Cream Soda tastes not entirely unlike A&W Cream Soda. Especially if you haven’t had real Cream Soda for a while.
Regular Diet Rite (the one that is supposed to taste like RC) is OK but I really like the flavored Diet Rite sodas. They beat the flavored carbonated waters all to hell. Zero calories, zero sodium, decent flavor.
Coke Zero, Sprite Zero, Fresca… I lost a LOT of weight giving up Coke and Snapple, and HATE diet sodas.
Another vote for Coke Zero. And my main shout out for Diet Dew.
I hate diet sodas, but can drink those two happily with lots of ice.
That and Crystal Light lemonade, though that doesn’t count - maybe if you made it with club soda?
If you like a black cherry diet, try Diet Dr. Pepper Berries and Cream, or Diet Dr. Pepper Cherry Vanilla.
I’m addicted to the berries and cream myself. Nom nom.
slips out to the fridge in the garage for a can
Try Trader Joe’s for Hansens. I’ll second the recommendation, it’s my favorite breakfast juice.
If there’s one you find acceptable, drink it and only it for a few weeks. After that, you’ll be accustomed to the flavor of the sweetener and will be able to branch out.
The trick is not to drink anything to reset your tastebuds. Eventually, the diets will taste “normal” and sugared drinks will taste weird.
Yes, that Coke Zero does taste way too much like regular Coke (bleah). So it may be just right for you!
Have you tried sweetened flavored carbonated water? I like the grocery store brand here, when I’m not drinking Crystal Light.
I am a long-time supporter of the Coke Zero, so add my vote.
I see you do not like Fresca. I don’t like the regular variety very much (I can take it or leave it), but I LOVE the peach flavored variety. Give that a try if you like peach flavoring. Delicious.
People say this all the time, but I have found it to be untrue for me. Diet soda never tastes normal (even the Coke Vanilla Zero that I praised in my previous post does not taste “normal”; I just happen to really like the “diet-y” taste in combination with the vanilla.) And even after weeks of abstaining, sugared drinks still taste really good to me.
Diet Dr. Pepper. It’s the only way to go.
Lots of Zero suggestions but I don’t think I saw one for Pibb Zero. Nectar of the Gods.
Another vote for Coke Zero…
And I also like Lipton Diet Raspberry White Tea.
Coke Zero tastes a lot like regular coca cola.
-FrL-
Diet Mountain Dew Code Red is good also.
I also really like the taste of Diet Barqs Root Beer, but unfortunately ther is no caffeine in it!
It really tastes just like the regular IMO. Why no caffeine?!
-FrL-
I’ll second (or third) the Diet Rite flavored sodas - my personal favorite is the tangerine, but the raspberry is pretty good, too.
Of course, I’ve been drinking diet soda so long that I can’t drink regular anymore, and that was before I discovered my corn allergy. 
Diet Dr. Pepper & Diet Mt. Dew (of both regular & Code Red varieties) are both good, as is Diet A&W.
I’ll also second the Hanson’s Diet Cream Soda - yum!
(I’ve been trying some new stuff lately because Himself is trying to lose weight, but can’t drink Nutrasweet, so we’ve been branching into Splenda. Personally, I exist on Diet Coke (the original) but he likes Diet Coke with Splenda, if you can find it.)